題解 | #統(tǒng)計復(fù)旦用戶8月練題情況#
統(tǒng)計復(fù)旦用戶8月練題情況
http://www.fangfengwang8.cn/practice/53235096538a456b9220fce120c062b3
select up.device_id,up.university, count(qpd.question_id) as question_cnt, sum(if(qpd.result='right',1,0)) as right_question_cut from user_profile as up left join question_practice_detail as qpd on up.device_id = qpd.device_id and month(qpd.date)=8 where up.university ='復(fù)旦大學(xué)' group by up.device_id
新get一個知識點,sum里面可以套用if,也可以用if函數(shù)的快速模式來寫